1. Field of the Invention
This invention relates to ballistically resistant and fire resistant composite articles, more particularly, for use in aircraft interiors, as well as other applications.
2. Description of the Related Art
Materials used in aircraft compartment interiors are regulated by Title 14 of the Code of Federal Regulations, Part 25. Until recently, the principal concern relating to such materials was fire resistance. However, in the wake of the aircraft hijackings of Sep. 11, 2001, by suicidal terrorists, protection against threats of other kinds has become a heightened concern. Principal among those concerns is security of the pilots and cockpit against firearms. A need exists for lightweight materials, for use in cockpit doors, that are resistant to penetration by handgun ammunition, and which also maintain current standards of fire resistance.
Fire resistant materials for aircraft interiors have been described in U.S. Pat. Nos. 4,780,359; 5,175,198; 5,714,419 and 5,972,512. U.S. Pat. No. 6,044,605 describes a door construction that, “ . . . can be made with fire-resistant and ballistic-resistant materials . . . ”.
U.S. Pat. No. 3,934,066 describes a fire-retardant laminate system suitable for application to a combustible or heat sensitive substrate comprising a flexible protective layer, and an intumescent layer comprising a porous cellulosic sheet material impregnated with an intumescent composition. The flexible protective layer may be a metal foil.
Materials possessing both fire resistance and ballistic resistance have been described in U.S. Pat. Nos. 4,822,439; 4,842,923; 4,929,651; 5,167,876; 5,215,813 and 5,480,706.
U.S. Pat. Nos. 4,822,439 and 4,929,651 describe composites comprising about 60% to about 75% by weight of woven magnesia aluminosilicate fiberglass roving impregnated with calcium hydroxide and an isophthalic thermoset polyester.
U.S. Pat. Nos. 4,842,923 and 5,167,876, describe composites comprising a plurality of layers of a balanced interlaced magnesia aluminosilicate glass fiber fabric in a matrix of a cured phenol formaldahyde resin having an areal density of at least 2.5 pounds per square foot.
U.S. Pat. No. 5,167,876, describes a composite comprising two or more layers, at least one of the layers being a network of fibers in a matrix and at least one of the layers being a fire retardant layer having endothermic properties on exposure to heat.
U.S. Pat. No. 5,480,706, describes a composite comprising a plurality of alternating first and second plies wherein the first ply comprises a network of high strength flammable fibers in a first matrix and the second ply comprises a network of fire resistant organic or inorganic fibers in a fire resistant matrix.
Each of the composite articles cited above represented progress toward the goals to which it was directed. However, none described the specific constructions of the present invention and none satisfied all of the needs met by this invention.
These earlier composite articles had the principal disadvantage of being largely comprised of relatively dense inorganic materials such as glass fibers. Such materials are not ideal for aircraft interiors where excess weight translates into unnecessary and costly fuel consumption. On the other hand, composite densities can be too low and take up excessive space. A need exists for composite materials exhibiting strength, toughness, ballistic resistance, and fire resistance combined with useful density.